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Diagnosing Psoriatic Arthritis in the Psoriasis Patient

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Speaker: Joseph F Merola, MD MMSc, FACR, FAAD

What are some key takeaways from the workshop you led?

So from the psoriasis and arthritis standpoint, at least from some of those workshops, I think we know that psoriatic arthritis is likely under diagnosed.

There’s a frequently quoted study that about 41% of patients or so at least in one study had previously undiagnosed psoriatic arthritis and then were diagnosed when they were seen by a rheumatologist. So, I think that underscores that it is still an under-diagnosed disease.

I think it’s important for the dermatologist to realize there are many domains of disease beyond just a swollen, red, tender joint. For example, something called enthesitis, which is inflammation at the site of tendon insertion into bone — which is a not uncommon aspect of psoriatic arthritishas the potential for having inflammatory back disease or spine involvement, so we talked about all of that during our session.

Then, really I think it’s our responsibility as dermatologists, who are the frontline for psoriatic disease in general, to really think about the comorbidities of disease, particularly for psoriatic arthritis, to be the ones who do the screening.

You know, we may not be extremely comfortable with it — and I think that’s normal since it’s not part of routine dermatology training to be thinking about the difference between inflammatory and non-inflammatory joint disease. But if we start to at least commit to screening our patients, we can get them to the right referral minimally. At best, I think we can start to get more comfortable with what the work of the diagnostic workup looks like and then ultimately what we would think about from a treatment perspective that would differ between skin and joint disease.

What is the psoriatic arthritis screening mnemonic that you came up with?

It’s based on “PSA” — colloquially how we how we discuss how we refer to psoriatic arthritis.

So, “p” is for pain: We remind the dermatologist to ask all of their psoriasis patients about joint pain. Then, to qualify that pain with “s” for stiffness, meaning joint pain and stiffness that is present for at least 20 or 30 minutes that then improves with activity and getting moving.

If the dermatologist can remember a second “s” for “sausage digit,” which refers to dactylitis, or a swollen digit. That’s very specific for psoriatic arthritis.

Then, “a” for an axial disease which is a reminder to ask about the inflammatory back pain. So, ask about back pain and then qualify it with the same “s,” the same stiffness, so back pain that actually is associated with stiffness that improves with movement improves with activity. That alone should prompt some formal screening, whether it’s the use of a screening questionnaire or validated screening tool or referral to a Rheumatologist.

How do treatment modalities differ between dermatologists and rheumatologists for PSA or psoriasis?

There are a couple of our therapies that really face one side more than the other. There are better there are better drugs for say psoriasis than psoriatic arthritis, or some that are approved only in one in one indication. So it’s important and a challenge sometimes to get the data across specialties. It would be really great — as a dermatology rheumatologist, or rheumatology dermatologist whatever you want to call it — I think one of the things I enjoy doing is trying to educate across discipline.

There are a few newer drugs including some that were approved just recently. There was a an oral JAK inhibitor, tofacitinib, that was approved which is a nice tool to have in our arsenal for psoriatic arthritis. It is at the present only approved for psoriatic arthritis, but it’s something our dermatology colleagues certainly should know about. It does have skin efficacy even if it’s not approved for skin, and we have other examples like that. So I think it’s it’s certainly helpful to for both sides to know what’s going on.

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